'show stats_histograms' and 'admin checksum table' behaviour differ between tikv and unistore

[tiancaiamao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

I'm testing paging protocol by running tidb UT with a real TiKV using this branch #35647

tiup playground nightly --mode tikv-slim
cd executor
go test -run ^TestShowPartitionStats$ -with-tikv 127.0.0.1:2379
go test -run ^TestAdminChecksumOfPartitionedTable$ -with-tikv 127.0.0.1:2379

2. What did you expect to see? (Required)

Test success

3. What did you see instead (Required)

Test case TestAdminChecksumOfPartitionedTable and TestShowPartitionStats run success on unistore, but fail on tikv.
The behaviour is different on those two store engine.

4. What is your TiDB version? (Required)

master

commit 47a4f3a017768dda0b9a826451486c5539bc8427 (HEAD -> master, origin/master, origin/HEAD)
Author: Weizhen Wang <wangweizhen@pingcap.com>
Date:   Wed Jun 29 20:16:40 2022 +0800

    *: enable unconvert (#35821)
    
    ref pingcap/tidb#35345